1. Field
The present specification relates to a terminal device that can be applied for a mobile phone-terminal device and a charging control method applied for the terminal device, and particularly relates to a charging control technology applied for a device provided with a solar battery.
2. Description of the Related Art
In the field of terminal devices including a secondary battery, such as mobile phone-terminal devices, terminal devices provided with a solar battery panel have been put to practical use. When the terminal device provided with the solar battery panel is left at a place which is illuminated enough to ensure an appropriate amount of power generated through the solar battery panel, the secondary battery provided in the terminal device is charged. Therefore, the battery duration of the terminal device is increased, for example.
A charger of a secondary battery provided with a solar battery has been disclosed in Japanese Unexamined Patent Application Publication No. 06-46536. According to Japanese Unexamined Patent Application Publication No. 06-46536, each of the temperature of the secondary battery and that of the solar battery (the environmental temperature) is detected and charging is stopped when the value of the difference between the secondary battery temperature and the solar battery temperature reaches a predetermined temperature. The technology disclosed in Japanese Unexamined Patent Application Publication No. 06-46536 allows for preventing the secondary battery being charged in a high-temperature state undesirable for the characteristics of the secondary battery.
When a solar battery panel is mounted on a terminal device such as a mobile phone-terminal device, the solar battery panel should be charged in the following use state. Namely, the terminal device is usually placed near a window irradiated with the sunlight so that the solar battery panel is irradiated with the sunlight as much as possible.
However, when the terminal device is directly irradiated with the sunlight, the temperature of the terminal device itself is increased, which may cause problems. More specifically, the secondary battery and/or the circuit components that are provided in the terminal device may be deteriorated.
When a battery of which temperature should be detected during the charging is used as the secondary battery, control is performed to stop the charging when the detected secondary battery temperature reaches the charging stop temperature so that the charging is not performed in the high-temperature state. The battery of which temperature should be detected during the charging includes a lithium-ion storage battery, a nickel metal hydride-storage battery, and so forth.
Thus, the charging itself is stopped based on the temperature to ensure the safety of the secondary battery. However, when the terminal device itself is left at a place irradiated with the sunlight, the temperature of the terminal device itself is kept high, which may deteriorate the secondary battery and/or other circuit components that are provided in the terminal device, which is hardly appropriate for the terminal device.